That constant smackdown when you see the interest charged to the mortgage account...

I pay more than the minimum payment in the vain hope that it genuinely reduces the loan term from 30 to under 20 years (which means I might still be alive when it's paid off!).

Current prediction is 22 years, so that's still an improvement.

The 'interest smackdown' is a constant reminder that someone always wants to take and doesn't want to give. 8-)